Hot start venting



Nov. 21, 1967 J. o. SARTO 3,353,801

I HOT START VENTING Filed April,26, 1966 44 J INVENTOR.

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United States Patent Office 3,353,801 Patented Nov. 21, 1967 3,353,801 HOT START VENTING Jorma 0. Sarto, Orchard Lake. Mich., assignor to Chrysler Corporation, Highland Park, Mich, a corporation of Delaware Filed Apr. 26, 1966, Ser. No. 545,389 7 Claims. (Cl. 261-43) ABSTRACT OF THE DISCLOSURE Apparatus to prevent the accumulation of fuel vapor in the mixing passage upstream of a carburetor throttle valve under hot operating conditions comprising vent means communicating such passage with the atmosphere and regulated by valve means therein operated by lnterengaging means on said throttle valve.

This invention relates to vehicle safety and in particular to automatic hot start vent means for venting the fuel-air induction conduit of an internal combustion engine at a location above the customary throttle valve when the latter is at its idle position.

When a typical internal combustion engine is operating, its conventional cooling system maintains the carburetor and associated fuel supply system comparatively cool, such that when the engine and its cooling system is temporarily turned off, the heat of the engine soaks into the carburetor and associated manifolding and proximate fuel system, causing the fuel therein to expand and vaporize at least in part so as to flow from the fuel bowl into the fuel-air induction conduit and often from the fuel pump supply line into the fuel bowl to flood the latter and the fuel passages to the induction conduit. Thereafter when an attempt is made to start the engine, accumulated fuel vapor in the induction conduit and supply passages thereto frequently causes hot starting difficulty by flooding the engine with raw fuel vapor.

A hot start vent to atmosphere from the induction conduit above the throttle valve is commonly employed to overcome this problem. In the event of a backfire in the inlet manifold at one of the engine cylinders, as for example during starting with the throttle open, the rapid pressure build-up sometimes blows fire back through the inlet manifold and carburetor induction condit, then through the hot start vent to ignite combustible materials that are sometimes allowed to accumulate adjacent the area of the vent opening. When the throttle is at its closed or idle position during starting, no backfire problem exists, and also the throttle itself also serves as a barrier to backfire. Reference herein to the throttle or throttle valve in the idle position means in the closed position, whereat. some air leakage in the induction conduit past the throttle valve sometimes exists.

7 An object of the present invention has been to provide an improved hot start vent system for an automobile induction conduit which automatically closes when the throttle is partially open from its idle position, so as to prevent backfire through the vent, and which automatically opens when the throttle is returned to its closed or idle position.

Other objects are to provide such a system which is readily adaptable for use with existing and customary structures; and to provide such a system comprising a hot start vent opening into the fuel-air induction conduit through the sidewall of the customary throttle body, a vertical shiftable vent closing valve contained in the throttle body and normally seated by gravity to close the vent, and a lifter element movable with the throttle valve to its closed or idle position to engage a portion of the vent closing valve which projects into the induction conduit through a slot in the sidewall of the throttle body, so as to unseat the vent closing valve and open the vent only when the throttle valve is moved to or adjacent its closed or idle position.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a fragmentary vetrical sectional view through a carburetor induction conduit, showing an embodiment of the present invention with the throttle valve closed and the vent valve open.

FIGURE 2 is a view similar to FIGURE 1, but showing a modification and also showing the throttle valve in a partially open position and the vent valve closed.

FIGURE 3 is a fragmentary sectional view taken in the direction of the arrows substantially along the line 3-3 of FIGURE 1.

FIGURE 4 is a fragmentary sectional view taken in the direction of the arrows substantially along the broken line 44 of FIGURE 1.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, a particular embodiment of the present invention is illustrated by way of example in a carburetorfor an automobile internal combustion engine. The carburetor may be of conventional construction and includes an air induction conduit 10 defined by several parts cast for example from aluminum or zinc alloys, including an upper air inlet or air horn section 11 which contains the usual choke valve and is adapted at its upper end for attachment with an air filter, an intermediate venturi section 12 containing a coaxial large venturi 13 and a coaxial small venturi 14, and a throttle body 15 which contains a throttle blade or valve 16 mounted on a diametrical shaft 17 journaled at opposite ends within the sidewalls of the throttle body 15. The throttle blade 16 is secured to the shaft 17 by screws 18 and controls the air flow inthe induction conduit 10 in accordance with conventional practice. The parts 11, 12, and 15 are suitably spaced by fibrous gaskets apertured so as not to obstruct the continuous induction conduit 10 extending through thes parts and are secured together by bolts, not shown. The base of the throttle body upper end of a cast steel fuel-air inlet manifold 19, which defines a continuation of the induction conduit 10 and conducts the fuel-air mixture to the engine cylinders. A suitable fibrous gasket also spaces the throttle body 15 from the manifold 19.

The intermediate venturi portion 12 may be cast integrally with a fuel bowl portion 20 into which fuel is supplied from a fuel pump and may be maintained at approximately a constant level 20a by a customary float controlled valve in the fuel supply line. Fuel from the bowl 20 is conducted through a metering element 21 and a main fuel supply conduit 22 to a well 23 formed in a sidewall portion of the induction conduit 10 defined by the intermediate section 12.

The fuel bowl 20 is customarily vented to atmosphere at a location within the air horn 11 and below the air fil ter. The fuel flow from bowl 20 to the well 23 is induced by the force of gravity and the pressure difierential existing on the fuel resulting from the low pressure in Well 23 when air is flowing in conduit 10. The well 23 opens into the air stream to the venturi section 12 by means of a 15 is supported by the metering orifice 24 at the upper end of an aeration tube 25, which extends into the well 23 and is provided with a plurality of sidewall openings 26. The upper portion of the well 23 is connected at a location above the normal fuel level 20a in the bowl 20 with a primary fuel nozzle 27 bymeans of a duct 28 in the support portion 29 for the small venturi 14. The support 29' is secured to the sidewall of the section 12 and cooperates therewith to define an upper portion of Well 23.

Upon opening of the throttle valve 16 while the engine is operating, the air flow in conduit induces a low pressure Within venturi 14 at the discharge end of nozzle 27, which causes the fuel level Within the well 23 to rise above the normal level 20a and enter the passage 28 and discharge through nozzle 27. The greater the air flow, the greater will be the fuel flow. As the fuel rises in the well 23, it is mixed with air supplied via the perforated tube and ispartially emulsified and vaporized, whereby further vaporizing in the main air stream in the induction conduit 10 is facilitated.

The fuel flow to well 23 via metering element 21 and conduit 22' is controlled in accordance with demand by a metering rod having its upper end secured to a piston 31 reciprocal in a vertical cylinder 32 and yieldingly urged upwardly by a coil spring 33. The lower end of cylinder 32 below piston 31 is connected by suitable conduit means (not shown) with the induction conduit 10 at a location below the throttle valve 16. Thus the piston 31 is urged downwardly with decreasing pressure downstream of the throttle valve 16, i.e., as the latter closes. When the throttle valve 16 progressively opens and the pressure downstream thereof increases, the metering rod 30 will be moved upwardly as aforesaid by spring 33. The lower end of metering rod 30' is guided by element 21 to progressively open or close the communication between fuel bowl 2'0 and conduit 22 in accordance with theupward or downward movement of rod 30.

When the engine is operating at the idle condition with the throttle valve 16 closed, fuel for engine idling is supplied downstream of the throttle valve 16- by means of an idle tube 34 which opens at its lower end through a metering port into the well 23. The upper end of idle tube 34 opens into an idle passage 35 which communicates with idle port 36 downstream of the throttle valve 16. The idle mixture is controlled by a manually adjustable screw 37'. The upper end of idle passage 35- communicates via a metering passage 39 with the idle air entering the venturi section 12 from the upper air horn 11 and supplies air which mixes with the idle fuel received from tube 34 to provide a combustible idle fuel-air mixture at port 36.

In order to increase the fuel supply from the idle system during the initial stages of opening of throttle valve 16 when the air flow through induction conduit 10 is insufficient to raise the level of the fuel within well 23 to the upper opening of discharge conduit 28, a transfer port 40 comprising a vertically elongated slot extends through the sidewall of the throttle body 15 from' the idle fuel passage 35 into the induction conduit 10 at a location extending from slightly below to somewhat above the upper edge of the throttle valve: 16 when the latter is at its closed or idle position. Accordingly, upon the initial opening of the throttle blade or valve 16, a greater portion of the slotted transfer port 40 will be exposed to supply fuelinto the: conduit 10 downstream of the throttle valve 16.

Inasmuch as the fuel system may be conventional, further details of construction and operation are not described herein. Reference is hereby made to Bail Patent 2,966,344 as if the description in the latter were incorporatedherein for a more complete description of an example of a carburetor fuel supply system suitable for use with the present invention.

After the engine has been operated in a hot condition and is temporarily shut-down, heat from the engine causes expansion and vaporization of the fuel in the main fuel supply system, such that raw fuel vapor frequently enters the induction conduit 10 above the throttle valve 16 via nozzle 27 and the vent from bowl 20 as aforesaid. Inasmuch as the fuel vapor is heavier than air, all air within the conduit 10 above the throttle valve 16 can be displaced by fuel vapors which frequently rises within the air horn portion 11 and even into the upper air filter. When it is thereafter attempted to start the engine, the column of raw fuel vapor above the throttle 16 must be pumped through the engine and exhausted before a combustible fuel-air mixture is supplied. In consequence, hot starting diificulty or flooding of the engine frequently results.

In order to avoid the accumulation of fuel vapors above the throttle valve 16,. a cylindrical valve guide passage or bore 41 is provided vertically in the sidewall of the upper portion of the throttle body 15 so as to intersect the induction conduit 10 along a vertical slot 42, FIGURES 3 and 4, which terminates at its lower end adjacent the lower edge of throttle blade 16 in the closed position shown, FIGURE 1. The lower end of the bore 41, which latter may be formed by casting during the initial fabrication of the throttle body 15, tapers at 43 to provide a coaxial valve seat adjacent the lower edge of the throttle valve 16 when the latter is at the closed position, FIG- URE' 1. Extending coaxially with the cylinder 41 through the seat 43 is a port 44 which communicates withthe inner end of a lateral vent duct 45.v The latter extends from port 44 horizontally through the sidewall of throttle body 15 to the atmosphere. A ball or spherical check valve 46 is confined within the cylinder 41 in vertically guided relation and is urged by gravity to a seated position at the tapered seat 43 so as to close. port 44, thereby to block communication between the induction conduit 10 and the atmosphere via slot 42, port 44, and duct 45. The diameter of ball 46 is only slightly less than the diameter of cylinder 41, so that a portion of ball 46 projects through slot 42 into conduit 10.

A radially extending valve lifter 47 is suitably secured, as for example by welding or soldering, to the upper surface of valve 16 and extends toward ball 46 to underlie the portion thereof which projects into conduit 10, thereby to raise and unseat the ball 46 from the port 44 when the throttle valve 16 is moved to its closed or idle position. Accordingly, fuel vapor which might otherwise collect within the chamber 10 above the throttle valve 16 is vented through slot 42 below the raised ball 46 and then through port 44 and conduit 45 to atmosphere. However, when throttle valve 16 is partially open, as for example during starting of the engine, ball 46 is seated at 43 to close port 44 and prevent the possibility of back-firing through vent duct 45, FIGURE 2.

The structures of FIGURES l and 2 are identical in concept and in operation, except that in lieu of vent duct 45 comprising a hole extending into the sidewall of throttle body 15,. the lower end or base of the throttle body- 15- isformed with a downwardly opening groove 45a extending outwardly from: the port 44. Thus when the throttle body 15 is clamped to the inletv manifold 19, the gasket separating these members cooperates with the groove or slot 45a to provide a vent passage similar in. all other respects to the vent conduit 45 of FIGURE 1. The structurecomprising the groove 45a opening downwardly at the base of the throttle body 15 enables certain economies in construction and may be readily formed. during the casting of the throttle body 15. However, the construction illustrated in FIGURE 1, comprising the conduit 45 contained entirely within the throttle body 15, has the advantage of dimensional stability and is independent of dimensional changes that might take place in the gasket. separating. the throttle body 15 from the manifold 19-.

Having thus described my invention, I claim 1. In a carburetor for an internal combustion engine, a throttle body, a fuel-air induction conduit extending through said throttle body, throttle valve means having a valve element in said conduit movable between idle and open positions for controlling fluid flow in said conduit, means for venting gases in said conduit above said valve element to asmospheric pressure comprising a valve guide passage within the sidewall of said throttle body and opening into said conduit at a location immediately above said valve element when the latter is in the idleposition, a vent duct communicating with said atmospheric pressure, a port connecting said guide passage and vent duct, the sidewall of said throttle body defining said guide passage also defining a valve seat around said port, Vent valve means shiftable within said guide passage for seating at said valve seat to close said port and block communication between said induction conduit and atmospheric pressure,

and interengaging means on said throttle valve means and vent valve means operable in response to closing of said valve element to said idle position for unseating said vent valve means from said valve seat to open said port and vent said induction conduit to said atmospheric pressure.

2. In the combination according to claim 1, an inlet manifold structure defining an inlet passage for conducting a fuel-air mixture to said engine and supporting the base of said throttle body seated thereon with the portion of the induction conduit in said throttle body aligned with said inlet passage, said vent duct being defined by both said manifold structure and throttle body and comprising a groove in the base of said throttle body confronting said manifold structure and extending from said port to the exterior of said throttle body.

3. In the combination according to claim 1, said guide passage extending vertically above said valve seat, and said vent valve means seating by gravity at said valve seat to close said port.

4. In the combination according to claim 3, said guide passage opening into said induction conduit at a slot in the sidewall of said conduit immediately above said throttle valve element at said idle position, and said interengaging means including a portion extending through said slot for shifting said vent valve means from said valve seat to open said port to atmosphere upon closing of said throttle valve element to said idle position.

5. In the combination according to claim 1, said guide passage opening into said induction conduit through a slot in the sidewall of said conduit immediately above said throttle valve element at said idle position, and said interengaging means comprising means extending through said slot.

6. In the combination according to claim 5, said valve guide passage extending vertically within the sidewall of said throttle body, said vent valve means being vertically shiftable within said guide passage and being normally urged by gravity force to close said port.

7. In the combination according to claim 6, said interengaging means comprising a portion operably connected with said throttle valve element for movement therewith and engageable with a portion of said vent valve means to open the latter upon said closing of said throttle valve element to said idle position, at least one of said portions extending through said s-lot upon said closing of said throttle valve element to said idle position.

References Cited UNITED STATES PATENTS 2,690,331 9/1954 Weldy 26l1 2,962,014 11/1960 Durler 26139 2,988,345 6/1961 Kolbe et al 26l50 2,995,351 8/1961 Brown et al. 261-39 2,996,051 8/1961 Mick 261 3,254,638 6/1966 Walker et a1. 261-41 HARRY B. THORNTON, Primary Examiner.

TIM R. MILES, Assistant Examiner. 

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE, A THROTTLE BODY, A FUEL-AIR INDUCTION CONDUIT EXTENDING THROUGH SAID THROTTLE BODY, THROTTLE VALVE MEANS HAVING A VALVE ELEMENT IN SAID CONDUIT MOVABLE BETWEEN IDLE AND OPEN POSITIONS FOR CONTROLLING FLUID FLOW IN SAID CONDUIT, MEANS FOR VENTING GASES IN SAID CONDUIT ABOVE SAID VALVE ELEMENT TO ASMOSPHERIC PRESSURE COMPRISING A VALVE GUIDE PASSAGE WITHIN THE SIDEWALL OF SAID THROTTLE BODY AND OPENING INTO SAID CONDUIT AT A LOCATION IMMEDIATELY ABOVE SAID VALVE ELEMENT WHEN THE LATTER IS IN THE IDLE POSITION, A VENT DUCT COMMUNICATING WITH SAID ATMOSPHERIC PRESSURE, A PORT CONNECTING SAID GUIDE PASSAGE AND VENT DUCT, THE SIDEWALL OF SAID THROTTLE BODY DEFINING SAID GUIDE PASSAGE ALSO DEFINING A VALVE SEAT AROUND SAID PORT, VENT VALVE 